Abstract The goal of this administrative supplement funding request is to create a unique resource of banked DNA, peripheral blood mononuclear cells, and plasma obtained from deeply phenotyped patients with Alzheimer?s Disease (AD) and agitation (AD+A) participating in S- CitAD, an adaptive design randomized controlled trial for Agitation in Alzheimer?s Disease. This resource will immediately be available to S-CitAD investigators for the measurement of specific blood biomarkers in meeting S-CitAD Specific Aims 2 & 3: to identify subgroups of participants most likely to respond to treatment with escitalopram, to a psychosocial intervention (PSI), or to relapse after initial remission of agitation when treated with a PSI. This resource will also be made available to other investigators interested in the study of AD+A to characterize biologic mechanisms underlying agitation, and/or to study the natural history of AD+A.